Abstract: Described are methods, systems, and apparatus, including computer program products, for verifying document and/or web page compliance to a subsidiary standard. A set of rules representing one or more aspects of the subsidiary standard are obtained. It is determined, using a first rule from the set of rules, if an element of the document is compliant with the subsidiary standard. A display of the document is generated in a browser application. If the element is compliant with the subsidiary standard, the element is displayed normally. If the element is not compliant, the element is displayed with a visual indicator.